1. Field of the Invention
This invention relates to a method for smelting reduction in an electric furnace for smelting and reducing material ores by making use of the heat of arc and, more particularly, to a method for smelting reduction in an electric furnace for smelting and reducing an oxide, which is high in melting point and hard to reduce, with high efficiency and high recovery.
2. Description of the Prior Art
In a prior art method, chromium steel such as high alloy steel and stainless steel has been manufactured as follows. First, a material is smelted in an electric furnace to manufacture molten metal. The molten metal is then decarburized with an argon-oxygen decarburization apparatus or a vacuum oxygen decarburization apparatus so as to obtain the predetermined concentration of carbon. Hereinafter, the argon-oxygen decarburization apparatus will be simply referred to as AOD, while the vacuum oxygen decarburization apparatus will be simply referred to as VOD. Cr is added by a way of charging ferro-chromium, which is an alloy of iron and Cr in an amount of 20 to 60 wt%, into the molten metal. This ferro-chromium is manufactured by the steps of charging lime stone and chromium ore of such oxide that it is hard to reduce and smelt into an electric furnace and then reducing the chromium ore with a reducing agent, into which primary slag smelted by electric power is charged.
However, the prior art method for manufacturing the chromium steel by the use of ferro-chromium involves the following problems.
(a) A great deal of electric energy is necessary to manufacture the ferro-chromium. PA1 (b) It is poor in stirring of molten metal performed by the use of a stirrer after ferro-chromium is charged into the molten metal, thus requiring a lot of time for smelting reduction. PA1 (c) The manufacture of chromium steel becomes extremely high in cost.